Redis实战之多用户聊天室

多客户端之间的通信，可采用消息推送和消息拉取两种方法。所谓消息推送，即采用publish/subscribe模式，但该方法要求用户必须在线才能接收到消息；所谓消息拉取模式，即由接收端自己拉取存储在某种邮箱里的消息。

数据结构

1、群

群ID计数器：（string）

ids:chat

群成员：（zset，包括群内所有成员及其拉取的最新消息ID）

chat:群ID Last_Message_ID 用户ID

消息ID计数器：（string）

ids:msg:群ID

群消息：（zset）

msgs:群ID 消息ID 消息内容

2、用户

群组：（zset，包括用户加入的群及从群内拉取的最新消息ID）

seen:用户ID Last_Message_ID 群ID

原理

1、建群

incr ids:chat

2、进群

2.1、获取最新群消息ID：

Current_Message_ID = get ids:msg:群ID

2.2、修改群成员集合，更新用户从群内拉取的最新消息ID：

zadd chat:群ID Current_Message_ID 用户ID

2.3、修改用户加入的群，更新用户从群内拉取的最新消息ID：

zadd seen:用户ID Current_Message_ID 群ID

3、退群

3.1、修改群成员集合：

zrem chat:群ID 用户ID

3.2、修改用户加入的群：

zrem seen:用户ID 群ID

3.3、清除群消息：

1）获取群成员集合中剩余成员数目：

Number = zcard chat:群ID

2）若 Number <= 0，则删除群消息ID计数器和群内所有消息：

del ids:msg:群ID

zremrangebyrank msgs:群ID 0 -1

3）若 Number > 0，则：

获取群成员集合中最小的score，最小score之前的消息必定已被所有用户拉取：

Min_Score = zrange chat:群ID 0 0 withscores

清除已被所有成员拉取的消息：

zremrangebyscore msgs:群ID 0 Min_Score

4、发送消息

4.1、创建群消息ID：

New_Message_ID = incr ids:msg:群ID

4.2、将消息添加到群消息集合：

zadd msgs:群ID New_Message_ID 消息内容

5、拉取消息

5.1、获取用户所加入的群信息（包括群ID和从群内最后拉取的消息ID）：

<群ID, Last_Message_ID> = zrange seen:用户ID 0 -1 withscores

5.2、遍历所加入的群，拉取所有群消息（并记录最大未读群消息ID：Max_Message_ID）：

zrangebyscore msgs:群ID Last_Message_ID+1 inf

5.3、修改群成员集合和用户加入群集合，更新用户从群内拉取的最大消息ID：

zadd chat:群ID Max_Message_ID 用户ID

zadd seen:用户ID Max_Message_ID 群ID

5.4、清除已被所有成员拉取的消息：

获取群成员集合中最小的score，最小score之前的消息必定已被所有用户拉取：

Min_Score = zrange chat:群ID 0 0 withscores

清除已被所有人阅读的消息：

zremrangebyscore msgs:群ID -inf Min_Score

实现

1、建群

int ChatManager::createChat()
{
// 分配群ID
redisReply *pRedisReply = (redisReply *)redisCommand(m_pRedisContext, "INCR ids:chat");
if (pRedisReply == NULL)
{
return -1;
}

int nChatID = pRedisReply->integer;
freeReplyObject(pRedisReply);

return nChatID;
}

2、进群

bool ChatManager::joinChat(int nChatID, QString &strUser)
{
//1、获取最新群消息ID
QString strMsgIDKeyName = QString("ids:msg:%1").arg(nChatID);
redisReply *pRedisReply = (redisReply *)redisCommand(m_pRedisContext, "GET %s", strMsgIDKeyName.toLocal8Bit().data());
if (pRedisReply == NULL)
{
return false;
}

int nLastMsgID = pRedisReply->integer;
freeReplyObject(pRedisReply);

//2、修改群成员集合，更新用户从群内拉取的最新消息ID
QString strChatKeyName = QString("chat:%1").arg(nChatID);
pRedisReply = (redisReply *)redisCommand(m_pRedisContext, "ZADD %s %d %s", strChatKeyName.toLocal8Bit().data(), nLastMsgID, strUser.toLocal8Bit().data());
if (pRedisReply == NULL)
{
return false;
}

freeReplyObject(pRedisReply);

//3、修改用户加入的群，更新用户从群内拉取的最新消息ID
QString strSeenKeyName = QString("seen:%1").arg(strUser);
pRedisReply = (redisReply *)redisCommand(m_pRedisContext, "ZADD %s %d %d", strSeenKeyName.toLocal8Bit().data(), nLastMsgID, nChatID);
if (pRedisReply == NULL)
{
return false;
}

freeReplyObject(pRedisReply);

return true;
}

3、退群

bool ChatManager::leaveChat(int nChatID, QString &strUser)
{
//1、修改群成员集合
QString strChatKeyName = QString("chat:%1").arg(nChatID);
redisReply *pRedisReply = (redisReply *)redisCommand(m_pRedisContext, "ZREM %s %s", strChatKeyName.toLocal8Bit().data(), strUser.toLocal8Bit().data());
if (pRedisReply == NULL)
{
return false;
}

freeReplyObject(pRedisReply);

//2、修改用户加入的群
QString strSeenKeyName = QString("seen:%1").arg(strUser);
pRedisReply = (redisReply *)redisCommand(m_pRedisContext, "ZREM %s %d", strSeenKeyName.toLocal8Bit().data(), nChatID);
if (pRedisReply == NULL)
{
return false;
}

freeReplyObject(pRedisReply);

//清除群消息
//3、获取群成员集合中剩余成员数目
pRedisReply = (redisReply *)redisCommand(m_pRedisContext, "ZCARD %s", strChatKeyName.toLocal8Bit().data());
if (pRedisReply == NULL)
{
return false;
}

int nMembers = pRedisReply->integer;
freeReplyObject(pRedisReply);

if (nMembers <= 0)
{
//群内无剩余成员
//4、删除群消息ID计数器
QString strMsgIDKeyName = QString("ids:msg:%1").arg(nChatID);
pRedisReply = (redisReply *)redisCommand(m_pRedisContext, "DEL %s", strMsgIDKeyName.toLocal8Bit().data());
if (pRedisReply == NULL)
{
return false;
}

freeReplyObject(pRedisReply);

//5、删除群内所有消息
QString strMsgKeyName = QString("msg:%1").arg(nChatID);
pRedisReply = (redisReply *)redisCommand(m_pRedisContext, "ZREMRANGEBYRANK %s 0 -1", strMsgKeyName.toLocal8Bit().data());
if (pRedisReply == NULL)
{
return false;
}

freeReplyObject(pRedisReply);
}
else
{
//群内还有剩余成员 清除已被所有成员拉取的消息
//6、获取群成员集合中最小的score，最小score之前的消息必定已被所有用户拉取
pRedisReply = (redisReply *)redisCommand(m_pRedisContext, "ZRANGE %s 0 0 WITHSCORES", strChatKeyName.toLocal8Bit().data());
if (pRedisReply == NULL)
{
return false;
}

int nScore = atoi(pRedisReply->element[1]->str);
freeReplyObject(pRedisReply);

//7、清除已被所有成员拉取的消息
QString strMsgKeyName = QString("msg:%1").arg(nChatID);
pRedisReply = (redisReply *)redisCommand(m_pRedisContext, "ZREMRANGEBYSCORE %s 0 %d", strMsgKeyName.toLocal8Bit().data(), nScore);
if (pRedisReply == NULL)
{
return false;
}

freeReplyObject(pRedisReply);
}

return true;
}

4、发送消息

bool ChatManager::sendMsg(int nChatID, QString &strMsgInfo)
{
//1、创建群消息ID
QString strMsgIDKeyName = QString("ids:msg:%1").arg(nChatID);
redisReply *pRedisReply = (redisReply *)redisCommand(m_pRedisContext, "INCR %s", strMsgIDKeyName.toLocal8Bit().data());
if (pRedisReply == NULL)
{
return false;
}

int nNewMsgID = pRedisReply->integer;
freeReplyObject(pRedisReply);

//2、将消息添加到群消息集合
QString strMsgKeyName = QString("msg:%1").arg(nChatID);
pRedisReply = (redisReply *)redisCommand(m_pRedisContext, "ZADD %s %d %s", strMsgKeyName.toLocal8Bit().data(), nNewMsgID, strMsgInfo.toLocal8Bit().data());
if (pRedisReply == NULL)
{
return false;
}

freeReplyObject(pRedisReply);

return true;
}

5、拉取消息

bool ChatManager::fetchMsg(QString &strUser)
{
//1、获取用户所加入的群信息（包括群ID和从群内最后拉取的消息ID）
QString strSeenKeyName = QString("seen:%1").arg(strUser);
redisReply *pSeenRedisReply = (redisReply *)redisCommand(m_pRedisContext, "ZRANGE %s 0 -1 WITHSCORES", strSeenKeyName.toLocal8Bit().data());
if (pSeenRedisReply == NULL)
{
return false;
}

//2、遍历所加入的群
for (int nIndex = 0; nIndex < pSeenRedisReply->elements; nIndex = nIndex + 2)
{
int nChatID = atoi(pSeenRedisReply->element[nIndex]->str);
int nNextLastMsgID = atoi(pSeenRedisReply->element[nIndex + 1]->str) + 1;

//3、拉取所有群消息
QString strMsgKeyName = QString("msg:%1").arg(nChatID);
redisReply *pRedisReply = (redisReply *)redisCommand(m_pRedisContext, "ZRANGEBYSCORE %s %d INF WITHSCORES", strMsgKeyName.toLocal8Bit().data(), nNextLastMsgID);
if (pRedisReply == NULL)
{
freeReplyObject(pSeenRedisReply);
return false;
}

if (0 == pRedisReply->elements)
{
continue;   //没有未读消息
}

//4、展示所有未读消息
int nMaxMsgID = 0;
for (int nMsgIndex = 0; nMsgIndex < pRedisReply->elements; nMsgIndex = nMsgIndex + 2)
{
QString strMsgInfo = pRedisReply->element[nMsgIndex]->str;
int nMsgID = atoi(pRedisReply->element[nMsgIndex + 1]->str);

// 展示消息

if (nMsgID > nMaxMsgID)
{
nMaxMsgID = nMsgID;
}
}

freeReplyObject(pRedisReply);

//5、修改群成员集合 更新用户从群内拉取的最大消息ID
QString strChatKeyName = QString("chat:%1").arg(nChatID);
pRedisReply = (redisReply *)redisCommand(m_pRedisContext, "ZADD %s %d %s", strChatKeyName.toLocal8Bit().data(), nMaxMsgID, strUser.toLocal8Bit().data());
if (pRedisReply == NULL)
{
freeReplyObject(pSeenRedisReply);
return false;
}

freeReplyObject(pRedisReply);

//6、修改用户加入群集合 更新用户从群内拉取的最大消息ID
QString strSeenKeyName = QString("seen:%1").arg(strUser);
pRedisReply = (redisReply *)redisCommand(m_pRedisContext, "ZADD %s %d %d", strSeenKeyName.toLocal8Bit().data(), nMaxMsgID, nChatID);
if (pRedisReply == NULL)
{
freeReplyObject(pSeenRedisReply);
return false;
}

freeReplyObject(pRedisReply);

//清除已被所有成员拉取的消息
//7、获取群成员集合中最小的score，最小score之前的消息必定已被所有用户拉取
pRedisReply = (redisReply *)redisCommand(m_pRedisContext, "ZRANGE %s 0 0 WITHSCORES", strChatKeyName.toLocal8Bit().data());
if (pRedisReply == NULL)
{
freeReplyObject(pSeenRedisReply);
return false;
}

if (pRedisReply->elements != 2)
{
continue;
}

int nOldMsgID = atoi(pRedisReply->element[1]->str);
freeReplyObject(pRedisReply);

//8、清除已被所有人阅读的消息
pRedisReply = (redisReply *)redisCommand(m_pRedisContext, "ZREMRANGEBYSCORE %s -INF %d", strMsgKeyName.toLocal8Bit().data(), nOldMsgID);
if (pRedisReply == NULL)
{
freeReplyObject(pSeenRedisReply);
return false;
}

freeReplyObject(pRedisReply);
}

freeReplyObject(pSeenRedisReply);

return true;
}